Products containing hexafluoroethane (i.e., hexafluoroethane products) are produced in various degrees of purity. One type of hexafluoroethane product, resulting for example from the fluorination of a trichlorotrifluoroethane, a dichlorotetrafluoroethane and/or chloropentafluoroethane, often contains significant amounts of chlorotrifluoromethane and/or fluoroform.
Various gaseous fluorine-containing compounds are utilized to etch silica type materials for use in integrated circuits, see e.g., A. J. Woytek, J. Fluor. Chem. 33, 331-334 (1986). A major use of hexafluoroethane is as a plasma etchant in semiconductor device fabrication. It interacts with the surface of the integrated circuit wafer, modifying it so as to lay down the electrical pathways and providing for the surface functionalities that define the integrated circuit. As manufacturers are continually trying to increase the number of functionalities packed per unit surface area, the increasing fineness of surface detail in turn requires greater precision and consistency of the effect the etchant has on the wafer substrate. Products of high purity are critical for this application. It has been found that even very small amounts of impurities can result in wide line width and thus less information bits per chip. Moreover, the presence of trace impurities, including but not limited to particulates, metals, moisture, and other halocarbons in the plasma etchant, even when only present in the part per million level, increase the defect rate in the production of these higher density integrated circuits. As a result there has been continually increasing market demand for higher and higher purity etchants, and an increasing market value of materials having the required purity. Consequently, identification of the offending impurities and their removal represents a significant aspect of preparing the fluorine-containing compounds for these applications.
Purification of halogenated hydrocarbon products has been the subject of considerable research. Of particular interest are the challenges presented in separating a halogenated hydrocarbon from materials such as impurities in the starting materials used to produce the halogenated hydrocarbon, excess reactants, and reaction by-products which are difficult to remove by standard separation methods such as distillation. Selective sorbents have been proposed for various separations. The effectiveness of separation using such sorbents varies according to the chemical components involved; and the successful design of sorbent systems is considered highly dependent upon experimental determination of whether the relative sorbencies of those compounds are suitable for such systems.